The invention relates to an electronic battery tester.
Current methods for determining the condition of a battery (e.g., a lead acid vehicle battery, such as an automotive battery) can use a high current typically require the use of heavy, bulky test equipment. The methods can also require that the battery have enough charge to perform the test. Other methods may use a smaller current, but these methods may depend heavily on the battery""s state-of-charge, thereby making it difficult to test a battery that is deeply discharged. Additionally, the current methods for determining a battery""s condition may take longer than is desired to perform a test.
In one aspect, evaluating the condition of a battery includes applying a load to the battery for a first time period of three milliseconds to ten seconds, measuring a first voltage at the end of the first time period, removing the load, measuring a second voltage at the end of a first recovery time period after removing the load, measuring a third voltage at the end of a second recovery time period after removing the load, and analyzing the condition of the battery. The second recovery time period can be longer than the first recovery time period.
Analyzing the condition of the battery can include calculating a dynamic internal resistance for the battery at the end of the second recovery time period, and determining the condition of the battery based on the dynamic internal resistance of the battery. In certain embodiments, analyzing the condition of the battery can include displaying a capacity of the battery, a state of charge of the battery, and an indication of pass or fail. The method can include inputting a capacity of the battery and selecting the load to apply to the battery based on the capacity. Inputting the capacity can include selecting between an input based on one of cold cranking amps, cranking amps, amp hours, or other rating standard.
In another aspect, an electronic battery tester device includes a housing containing a load, a switch, cables exiting the housing for making electrical contact with terminals on the battery and contacting the switch, and an analyzing component that is structured and arranged to analyze the condition of the battery at the end of a first recovery time period and a second recovery time period. The switch applies the load to the battery for a first time period of between three milliseconds and ten seconds and removes the load from the battery. The analyzing component can include a calculating component that is structured and arranged to calculate the dynamic internal resistance for the battery and a determining component that is structured and arranged to determine the condition of the battery based on the dynamic internal resistance of the battery.
Implementations may include one or more of the following features. For example, the second time period may include a first recovery time period and a second recovery time period, where the second recovery time is longer than the first recovery time period. The first recovery period can be eight milliseconds to fifteen milliseconds, or ten milliseconds. The second recovery period can be forty milliseconds to eight hundred milliseconds, or sixty milliseconds. The condition of the battery may be analyzed by calculating a dynamic internal resistance for the battery and determining the condition of the battery based on the dynamic internal resistance of the battery. The load may be between eighty amps and one hundred amps and may be based on inputting a rating system and a capacity for the battery being tested.
The method and tester carry out a single load, dynamic internal resistance measurement. The method and tester can obtain battery condition results within one second, and with high precision. The tester and method can reduce or eliminate the amount of heat generated during testing and is not affected by magnetic fields generated by other devices located nearby.
These general and specific aspects may be implemented using a device, a method, or a computer program, or any combination of devices, methods, and computer programs. For instance, one implementation may include a hand-held electronic battery tester device. The device may be used for evaluating a battery (e.g., lead acid automotive battery).
Other features and advantages will be apparent from the description and drawings, and from the claims.